Thursday, 14 October 2010

HOWTO: Syncing your /home with a server

Do you have a storage server where you keep your files? Do you think it would be a neat idea to keep a copy of your user files (home directory) on that storage in case your laptop or desktop suffers some sort of a catastrophe? Would you like an approximation of Windows roaming profiles?

If you answered yes to any of the above then read on! (However you should read the disclaimer at the end of this post.)

* Ubuntu (Tested with 10.04.1 Lucid but should work with any version)

* You must have passwordless SSH configured between the client and server users on the two hosts.
* rsync and openssh-server are installed on both hosts.

b) On the server;

The server part is pretty simple. First we will login as the root user;

sudo -i

We need a place to store the copies of the home folders. Create a folder;

mkdir -p /store/homes

Go back to the client;

Now assuming that we have keyless access to our server from the client we just need a script to do the syncing.

Create a script in /etc/init.d

root@hack:~# vi /etc/init.d/homesync
# Provides: homesync
# Required-Start: $remote_fs $syslog
# Required-Stop: $remote_fs $syslog
# Default-Start: 2 3 4 5
# Default-Stop: 0 1 6
# Short-Description: sync homes at startup and shutdown
# Description:


case $MODE in

rsync -parv --inplace $TARGET /home/

rsync -parv --inplace --exclude-from=$EXCLUDE --delete /home/ $TARGET


Note: Of course you need to change TARGET= to suit your own environment. Also, if your SSH server is listening on a non standard port you will need to modify the rsync command as per this post

Make the script executable;

chmod +x /etc/init.d/homesync

If you look carefully, you will notice that the script will refer to /root/excludes.rsync for any files or folders that it should avoid syncing. We should create that file;

touch /root/excludes.rsync

Now, there are no files on the server yet so we should do an initial sync.
WARNING: If this is not the first (ie primary) client that you are setting this up on then don't run the following command as is or else it will wipe out the "backup" that is already on the server. In such a case you need to replace the "stop" in the command with "start" in order to retrieve the primary files from the server instead.

Perform an initial sync;

/etc/init.d/homesync stop
Note: Depending on how much stuff you have in your user homes this may take some time. You should also ensure that you have enough space to fit everything!

OK, assuming everything is working, the final step is to make sure the homesync script executes when the system stops and start. We do that with the update-rc.d command;

sudo update-rc.d -f homesync defaults

That's it. You can test your setup by adding or altering a file in your home folder and then shutting down your system. If you check the server you should see your changes appear there after it shuts down. If you delete or alter the file again on the server the change should appear on the client after reboot.

If you want to exclude particular files or directories then you may list them in the exludes.rsync file we created earlier.

Here is a sample list;


DISCLAIMER: Be very careful using this setup in a multiuser environment where there is more than one PC (in use) at any one time. If a user is logged in on more than one PC then it is possible that they could lose data. Be sure you understand the limitations of this system before proceeding down such a path. Also note that the script only executes at startup and shutdown so if the PC is rarely restarted then this system will be of little value. I recommend using it for a simple home network only. It is not flexible or robust enough for use in a corporate network. And one final note, this does not work if you connect to the server using a wifi connection due to the way Ubuntu connects and disconnects after the user logs in. Any script such as this one that runs at boot time will not be able to connect to the network in order to do the sync. In such scenarios you could consider using a cron job or syncing manually.

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